During servicing of refrigerant circuits, such as the air conditioning system of a vehicle, the refrigerant is recovered, recycled and recharged. As the refrigerant capacity of mobile air conditioning system becomes increasingly small due to environmental regulations, it is increasingly more difficult to measure the accuracy of the refrigerant charge because any residual refrigerant in a tube or hose will change the accuracy of the measurement.
Typically, when charging the air conditioning system with refrigerant, the pressures of the air conditioning system are displayed to the user on direct pressure measuring analog gauges on the control panel of the machine. It is necessary to have tubes to transmit the pressure from the air conditioning system, at the end of the hoses, to the direct pressure measuring gauges on the control panel. Typical service hoses are 8 feet long, therefore, the tubes that are used to transmit pressure to the gauges would have to be at least the same length. Hence, the volume of the refrigerant in the long pressure tube would be significant enough to decrease the accuracy of the refrigerant charge.
Accordingly it is desirable to provide a diagnostic service equipment capable of accurately measuring the charge accuracy of an air-conditioning station using electrically driven analog-display pressure gauges.